Choosing a flexible sensing film: range, array density and encapsulation
Three parameters constrain each other. Range headroom, array density and encapsulation are usually selected in the wrong order — here is the sequence that holds up in the field.
PDRELTEST Engineering · 8 min read · 2026-10-21
Three questions come up in almost every specification meeting: how much range headroom do we need, how dense should the array be, and will encapsulation cost us sensitivity? The three parameters constrain each other — there is no optimum, only a match to your measurement objective.
1. Range: size it against the peak, not the average
Many projects fail on a single detail: the range was chosen from the average working pressure, and one start-up transient pushed the film into saturation.
Specify roughly 1.5× the actual peak pressure. Too much headroom reduces sensitivity and signal-to-noise ratio; too little means the film works near saturation, where return-path consistency degrades.
| Pressure characteristic | Band within 400–6000 kPa | Typical use |
|---|---|---|
| Low end of the window | 400–1500 kPa | Assembly surfaces, gripping, tactile work |
| Mid window | 1500–3000 kPa | Press fitting, fixture loading |
| Upper end | 3000–6000 kPa | Blade surfaces, structural parts |
2. Array density: match the feature scale
More points is not automatically better. The criterion is the size of the pressure feature you need to resolve: for an overall trend across a surface, 20–30 mm pitch is usually enough; to locate a local hotspot, pitch may need to drop to 5–10 mm.
Density costs more than film area — it adds conductors, channels and on-site routing. That is why many designs that work in the lab cannot be installed in the field.
3. Encapsulation: what survives the first winter
Outdoor encapsulation has to handle water ingress, temperature cycling, UV and abrasion — while staying bonded to a curved surface. Too thick and it flattens the pressure field; too thin and it protects nothing.
Our rule: fix the encapsulation process first, then the film thickness. What you measure is the response of the encapsulated stack, not of the bare film.
4. A simplified selection path
- Surface size and curvature → film geometry and zoning
- Peak pressure → range
- Feature scale to resolve → pitch and point count
- Environment and duration → encapsulation and adhesive
- Channel count and routing → check feasibility against steps 1–3
FAQ
Size the range at roughly 1.5 times the actual peak pressure. An oversized range costs sensitivity; an undersized range saturates and degrades repeatability.
No. Array density should match the scale of the pressure feature you need to resolve. Excess density multiplies cabling complexity and acquisition cost.
Singly-curved surfaces are straightforward. Doubly-curved surfaces require zoning or slitting, depending on the radius and the acceptable measurement error.
Written by our application engineering team and reviewed by the engineering lead. Figures are based on lab and field experience; project-specific conditions should be assessed individually.